ASICS are arrays of similar components that are manufactured in an integrated circuit for later conversion into a specific logical design. ASICs thus provide a relatively inexpensive way to create various complex designs using the same well-settled design components repeatedly.
The various components are interconnected by providing a netlist to the customer of the ASIC. The netlist is a list of which pads, terminals or nodes of components of the ASIC are to be connected to others to realize the complex logic circuit. The customer can either use the netlist to interconnect the components, or the ASIC supplier can interconnect the components by using the netlist, providing the completed logic circuit to the customer. The interconnection can be done by any of several well-known techniques, such as by metallization to provide conductive paths between the pads, terminals or nodes, or by blowing fuses to remove conductive paths between undesired pads, terminals or nodes.
The customer typically will have specified the logical operation to be conducted by the final circuit, but is not given the schematic diagram of the circuit that implements the logical operation. The object of providing the netlist but not the schematic diagram is to protect the supplier from persons learning of the circuit and copying and/or modifying the circuit in a manner unintended by the supplier, depriving the supplier of sales of value added modifications, for example. For example, a design may provide all possible features of a system, yet the netlist may specify connection of components to satisfy a low price purchase of only some of the features. By knowing the true design, a third party could manufacture the ASIC, changing the netlist a relatively small extent to provide all of the features, thus trading on the original supplier's development costs.
It is possible with today's computer aided design software programs and with some skill to recreate the schematic of the logic circuit, and provision of the netlist makes the supplier vulnerable to others, as noted above.